Maybe a time lag would be useful? Something along the lines of: “versions of a story appearing within a week of the first post should be attached to the original as replies, versions a week or more afterwards [that present substantial developments] can start a new thread”? It likely wouldn’t be possible to enforce a substantial development rule, but there can be dramatic changes to the story over time. The Titan submersible business was a different story on the Thursday than it was on the Monday of the same week, for example (which breaks my own rule, of course, but I think it’s an easy example) and there will probably be another story once some more analysis has been done. I agree that it would be better to have fewer threads to get a richer conversation, but I think there are limits to what actually fits in a single thread.